Digital measuring scanner

Abstract

A digital measuring scanner for scanning and plotting the distribution of a measured variable across a scanning pattern in a digital scanning tunnel microscope. The scanner includes a sensor for the measured variable that scans the scanning pattern line by line, a differentiating circuit connected to the output of the sensor, an ADC (analog to digital converter) connected to the output of the differentiating circuit, a computer for producing image signals connected to the output of the ADC and an output device for the image signals that is connected to the output of the computer. The computer is designed such that it can reconstruct absolute output values based on the digital differentiated measuring signal with the absolute output values corresponding to the values of the measured variable in the scanning points and that produces image signals based on these values.

1 . Digital measuring scanner for scanning and plotting the distribution of a measured variable (h) across a scanning pattern ( 10 ), in particular digital scanning tunnel microscope comprising: 
 a sensor ( 12 ) for the measured variable (h) that scans the scanning pattern ( 10 ) line by line;    a differentiating circuit ( 14 ) that is connected to the output of the sensor ( 12 );    an ADC ( 16 ) that is connected to the output of the differentiating circuit ( 14 );    a computer ( 18 ) for producing image signals (B A ) that is connected to the output of the ADC ( 16 ) and whose design is such that it can reconstruct absolute output values (A) based on the digital differentiated measuring signal (S D ) with the absolute output values corresponding to the values of the measured variable (h) in the scanning points and that produces image signals (B A ) based on these values; and    an output device ( 20 ) for the image signals (B A ) that is connected to the output of the computer ( 18 ).    
     
     
         2 . Measuring device according to    claim 1    wherein the differentiating circuit ( 14 ) has a capacitor ( 34 ) and a resistor ( 36 ).  
     
     
         3 . Measuring device according to    claim 1    further comprising a circuit ( 22 ) for signal matching between the differentiating circuit ( 14 ) and the ADC ( 16 ) whose design is such that it amplifies the differentiated signal (U D ) by a preset factor and increases it by a preset signal level.  
     
     
         4 . Measuring device according to    claim 1    wherein the computer ( 18 ) carries out the following steps for the purpose of reconstructing the absolute output values (A): 
 calculates a first intermediate value (Z 1 (n,m)) for each scanning point by determining a mean value (e) based on the values (E) of the digital, differentiated measuring signal (S D ) in the scanning points and by subtracting this mean value (e) from the value (E(n;m)) in this scanning point;  
 calculates a second intermediate value (Z 2 (n,m)) for each scanning point by applying the following formula in each line of the scanning pattern ( 10 ) for the scanning point at the beginning of this respective line:  
   Z   2 (1 ,m )= Z   1  (1 ,m),    
  and in that the following iteration formula is applied for each additional scanning point of this line:  
   Z   2 ( n,m )= Z   2 ( n  −1 ,m )+ Z   1 ( n,m )− Z   1 ( n −1 ,m )× exp (−Δ n /τ),  wherein: m is the index for the lines on the scanning pattern; n is the index for the scanning points in a line, and n=1 represents the beginning of the line; Z 2 (n,m) is the second intermediate value to the n-th scanning point in the m-th line; Z 1 (n,m) is the first intermediate value to the n-th scanning point in the m-th line; An is the index difference between two adjacent scanning points of a line and Δn=n−(n−1)=1 applies; and τ is a fading constant that represents the fading behavior of the differentiating circuit;    
 calculates a third intermediate value (Z 3 (n,m)) for each scanning point by applying the following formula for the scanning points of the first line of the scanning pattern ( 10 ):  
   Z   3 ( n ,1)= Z   2 ( n ,1),  
  and initially calculates the difference (D(n,m)) in each additional line for the scanning points of this line based on the following formula:  
   D ( n,m )= Z   2 ( n,m )− Z   2 ( n,m −1),  wherein: m is the index for the lines on the scanning pattern and m=1 represents the first line of the scanning pattern; n is the index for the scanning points in one line; Z 2 (n,m) is the second intermediate value for the n-th scanning point of the m-th line and D(n,m) is the differential value for the n-th scanning point of the m-th line,    
  then determines a mean value (d(m)) based on the differential values (D(n,m)) of this line and finally adds this mean value (d(m)) to each second intermediate value (Z 2 (n,m)) in the scanning points of this line; and  
 calculates the absolute output value (A(n,m)) for each scanning point by selecting the minimum from all third intermediate values (Z 3 (n,m)) and subtracts this minimum from the third intermediate value (Z 3 (n,m)) at this scanning point.  
 
     
     
         5 . Measuring device according to    claim 4    wherein the mean value (e) is determined by means of arithmetical averaging based on the values (E) of the digital differentiated measuring signal (S D ).  
     
     
         6 . Measuring device according to    claim 4    wherein the mean value (d(m)) is determined by means of arithmetical averaging based on the differential values (D(n,m)) of a line.  
     
     
         7 . Measuring device according to    claim 4    wherein the mean value (d(m)) is determined by means of averaging weighted by frequency (F(D)) based on the differential values (D(n,m)) of a line.  
     
     
         8 . Measuring device according to    claim 4    wherein the fading constant (τ) can be entered into the computer ( 18 ).  
     
     
         9 . Measuring device according to    claim 4    wherein the differentiating circuit ( 14 ) has a capacitor ( 34 ) and a resistor ( 36 ) and in that the computer ( 18 ) calculates the fading constant (τ) by dividing the synchronization period duration (P) of the ADC ( 16 ) by the capacity (C) of the capacitor ( 34 ) and by the resistance value of the resistor ( 36 ).  
     
     
         10 . Measuring device according to    claim 1    wherein the output values (A) are presented as a contour line diagram.  
     
     
         11 . Measuring device according to    claim 10    wherein the output values (A) are represented by brightness and/or the color of the corresponding pixels in the contour line diagram.